Television as a business makes money by selling audiences to advertisers and audience measurement, in particular by Nielsen Ratings, is used for determining the cost of advertising spots in television programs. The ratings have been gathered either by using surveys, where a viewer keeps a diary of watched programming in exchange for a fee, or by using a meter device coupled in selected homes with TV set for gathering the information automatically and transmitting it to a central location through a phone line. A criticism of the system is that it fails the important criteria of sample in the statistical sense. The sample, in fact, is not random because generally viewers are reluctant to accept diaries or meters and as a result, only those who agree are included in the sample. Another problem is the sample size: meter installation is expensive and Nielsen Media Research Inc., the major player in this area, has been able to sample only a few thousand households in selected regions around the world.
Digital cable and satellite terminals, so called set top boxes, can collect audience data directly, automatically and in a real-time manner. U.S. Pat. No. 6,735,775 to Massetti discloses an audience rating system for digital television and radio using identification codes in control streams of time-multiplexed digital transmissions. When a television or radio receiver is tuned into a channel, an identification code for media stream of the channel is extracted from the control stream, and recorded along with the time.
Collection of audience data in multifunctional digital receivers is not a problem, the problem is data delivery from the receivers to a central location. In a broadcasting system, all receivers that are tuned to the same channel are receiving the same signal and therefore the number of receivers is not limited by the system throughput called “bandwidth”. But amount of data transmitted from the receivers to a central location over a return pass is proportional to the number of receivers and is limited by bandwidth of the return pass. With too many active receivers the system may go down because of overload. Moreover the return pass, which is provided by two-way cable or phone line or wireless network, is primarily designated for Internet access, video on demand and telephony rather than for audience measurement.
U.S. Pat. No. 4,584,602 to Nakagawa discloses a system for automated collection of audience data wherein each receiving terminal is waiting a period of time necessary for other terminals within the system to transmit their data back to the broadcasting station and then automatically dials a telephone number at the station. After all terminal units have called in, the results are tabulated.
U.S. Pat. No. 5,600,364 to Hendricks et al. teaches a cyclic polling in a system with a digital cable headend that gathers data on what programs are watched as well as viewer information. A control signal from the headend is transmitted to each set top terminal to initiate upstream data from the terminal. The headend interrogates each terminal sequentially, one by one. Once all terminals have been given permission to transmit status reports, a cycle is complete and a new cycle begins.
U.S. Pat. No. 7,003,790 to Inoue et al. discloses an audience rating data acquisition apparatus that transmits information to the notification destination over a telephone line. The transmission time is assigned at random and not in response to a data transfer request received from a device external to the apparatus. The random number generator uses the telephone number as the key.
U.S. Pat. No. 7,409,212 to Grilli et al. discloses a method and apparatus to track count of broadcast content recipients in a wireless telephone network. In order to avoid the base station overload by all mobile stations trying to register simultaneously, the system spreads the registration in time using a “wait factor” that guides mobile stations in determining how much of a delay to institute before registering. The wait factor prescribes an average wait of an experimental, Gaussian, geometric, normal, or other statistical distribution.
U.S. Pat. No. 6,530,082 to Del Sesto et al. discloses a configurable monitoring of program viewership. While conventional monitoring depends on the pre-selection of a number of households that have the monitoring equipment, the patent teaches ability to dynamically configure which households are included in a particular monitoring event and ability to control sample size to avoid overloading the response capacity of the monitoring system and enhance the precision with which viewership data is collected. Thus for a very popular television program watched by millions of viewers, the monitoring may be configured so to create 1% sample of about 10,000 viewers. For a less popular television program with only about 100,000 viewers, the monitoring may be configured so to create a 10% sample. In such a system, each broadcast receiver generates a random number or uses other selection criteria in order to determine whether it is in the responding group.
U.S. Pat. No. 7,356,751 to the applicant discloses a method that incorporates audience measurement in an error handling technique. In the system, the transmitter gets an audience estimate by sending a packet with a wrong error checking value and processing the response of receivers. It is desirable however to separate audience measurement from error handling for the reason that although video data is transmitted in packets, packet recovery currently is not used in television. While a computer program delivered with a transmission error does not work, an error in video data could be localized so that viewers see it just as a glitch on the screen. Meanwhile audience measurement is important for advertising.